1. Field of the Invention
This invention relates to an optical apparatus such as a camera, lens, intermediate tube, etc., having mounts for coupling.
2. Description of the Related Art:
The conventional mounts for the camera and the lens have been made either by machining metal to the shape, or after having sintered stainless steel material, by applying treatments in portions.
For this reason, the conventional mounts for the camera and the lens require a long manufacturing process, thus being parts of very high price.
FIGS. 4(a) and 4(b) show an example of metallic mount for camera, with FIG. 4(a) being a front view and FIG. 4(b) being a back view. This mount is of the bayonet type. A plurality of pawl portions 4a are formed on the inner periphery of the mount 4. Protuberances 4b are provided on the back side of these pawl portions 4a.
Also, a plurality of screw-threaded holes 4d at which the mount 4 is to be fixedly secured to the camera body (not shown) are formed in the circumferential direction, and the abutment surface 4e at which the mount 4 abuts on a mount 3 of the photographic lens shown in FIG. 3 is formed to an even plane. The mount 4 for camera is provided with a mount spring 2 shown in FIG. 2. When the photographic lens is attached to the camera body, the mount spring 2 abuts on portions of the lens mount 3 and functions to press the photographic lens against the camera body, as the spring portions 2a work as springs. The lens mount 3 has pawl portions 3a which are arranged to abut on the spring portions 2a of the mount spring 2 to receive the forces therefrom, a so-called abutment surface 3b which is arranged to abut on the abutment surface 4e of the camera mount to determine the axial position of the photographic lens, and a concave portion 3c formed therein. Incidentally, among the photographic lenses, there are some which do not have the concave portion 3c.
The state in which the photographic lens has been attached to the mount 4 for camera made of metal constructed in such a way is shown in FIG. 5. Coupling of the lens mount 3 of the photographic lens with the mount 4 for camera is to move the lens mount 3 from the left of FIG. 5 toward the mount 4 for camera to be fitted therein, adjust the pawls 3a of the lens mount 3 to the pawlless portions 4g of the mount 4, move the lens mount 3 until the abutment surface 3b of the lens mount 3 abuts on the abutment surface 4e of the camera mount 4, and rotate the lens mount 3 until it is stopped by a stopper member (not shown). At this time, the pawl portions 3a of the lens mount 3 are urged by the spring portions 2a of the mount spring 2, and receive the bias force of direction to the left in FIG. 5. The abutment surface 4e of the mount 4 for the camera abuts on the abutment surface 3b of the lens mount 3, and the axial position of the photographic lens relative to the camera body is determined.
By the way, since the conventional mount for camera is made of metal, its manufacturing process is long, resulting in very expensive parts.
So, it may also be considered to mold the mount by using plastic material. However, the member molded of plastic material is weak in its surface hardness as compared with metallic material. When the photographic lens is attached to the camera, that surface which abuts on the metallic mount 3 of the lens side, particularly the force receiving surface, is apt to get scratches, which may extremely degrade the camera product.
That is, during the photographic lens attaching work, the lens mount 3 rotates, while receiving the force of the mount springs 2. Because a large frictional force exists between the mount 4 for camera and the lens mount 3 made of metal, the mount 4 for camera, too, must be made of a material having an equal or higher surface hardness than that of the lens mount 3. Otherwise, the mount 4 for camera would take large scratches. In the case of the lens mount not having the concave portion 3c, the scratches occur at random. In the case of the lens mount having the concave portion 3c, they occur in ring shapes. Thus, the state of scratches becomes conspicuous as differing from the non-contact portions. In either case, the camera product would be extremely degraded.